Son Doong Cave, Vietnam Currently, the worlds largest cave! Sơn Đoòng cave is a cave in Phong Nha-Kẻ Bàng National Park, Bố Trạch district, Quảng Bình Province, Vietnam. Currently the biggest cave in the world, the cave is located near the Laos-Vietnam border It has a large fast-flowing underground river inside. [1] National Geographics Interactive Cave Exploration. Photo: Carsten Peter Caves Affiliate Link National Geographic